Distribution And Near-/Mid-Infrared Emission Properties Of Rare-Earth Ions In Oxyfluoride Glass-Ceramics

Laser operating in the near-and mid-infrared wavelength region has important applications demand in the field of medical treatment,communication,remote sensing,biological engineering and pollution monitoring.Due to the rich of energy levels,rare-earth ions doped laser materials have been considered as one of the effective way to obtain infrared coherent light.To improve the quantum efficiency of rare-earth ions,the phonon energy of matrix should be as low as posssible.Oxyfluoride glass-ceramics,which is composed of fluoride nanocrystals and oxide-like matrices,integrate the advantages of fluoride and oxide glasses.Fluoride nanocrystals in the glass matrices provide the low phonon energy environment for optically active ions,and the glass matrices which are close to the oxide glasses,guarantee the good chemical and mechanical properties of these composites materials.Due to the preferential incorporation of rare-earth ions into the fluoride nanocrystals,it has been widely accepted that fluoride nanocrsytals formed in the glass can suppress the multi-phonon relaxation of excited rare-earth ions.When the concentrations of rare-earth ions are high,average distance among them will be short and efficient energy transfer processes will occur easily,leading to the efficient up-conversion or concentration quenching of the emission from certain energy levels of rare-earth ions.To realize the efficient infrared emission from rare-earth ions,it is essential to explore the distribution of rare-earth ions inside the fluoride nanocrystals.In chapter 1,reviews the research progress of near-/mid-infrared laser and rare-earth ions doped oxyfluoride glass-ceramics.We introduced the effect of distribution of rare-earth ions on its optical properties and spectrum theory of rare-earth ions.To control the distribution of rare-earth ions inside the fluoride nanocrystals and prepare oxyfluoride glass-ceramics with high transmittance in mid-infrared wavelength region,works were done mainly as follows:?1?Effect of YF₃ co-doping on formation of fluoride nanocrystals and optical properties of Er³⁺ions were investigated systemtically.XRD patterns,electron energy loss spectrum,absorption spectra and emission sprectra showed that addition of Y³⁺ions can promote the formation and incorporation of Er³⁺ions into fluoride nanocrystals,and decreae the effective concentration of Er³⁺ions inside the fluoride nanocrystal.As a result,energy transfer between Er³⁺ions were suppressed and enhanced 0.98?m and 2.73?m emissions were obtained.With optimization of rare-earth ions doping concentration,performance of 2.73?m emission from Er³⁺ions was systemically evaluated.?2?With the doping concentration of rare-earth ions fixed at 1.50 mol%,effects of substitution of Tm³⁺ions by Y³⁺ions and co-doping with Eu³⁺/Tb³⁺ions on 1.47?m emission properties were studied.To guarantee the formation of fluoride nanocrystals and decrease the effective concentration of Tm³⁺ions inside the fluoride nanocrystals,Y³⁺ions were co-doped to substitute Tm³⁺ions.As a result,energy cross relaxation between Tm³⁺ions was suppressed and efficient 1.47?m emissions were obtained.Additional doping of these specimens with Eu³⁺and Tb³⁺ions lead to the depopulation of Tm³⁺:³F₄ level,and resulted in further enhanced 1.47?m emissions from Tm³⁺:³H₄ level.?3?Based on the 55SiO₂-20ZnO-25BaF₂ galsss system,optical non-active rare-earth ions were co-doped to substitute the Ho³⁺ions for formation of BaF₂nanocrystals.XRD patterns,TEM image confirmed the formation of BaF₂nanocrystals.Incoproation of Ho³⁺ions into fluroride nanocrystals were confirmed by the absoprption spectra and the Judd-Ofelt parameters.Emission spectra,fluorescecence lifetime and luminescence rise curve of Ho³⁺:⁵I₈?⁵I₆ transition showed that effective concentration of Ho³⁺ions inside the BaF₂ nanocrystals decreased with the substitution of Ho³⁺ions by Y³⁺ions,and as a result,energy cross relaxation between excited Ho³⁺ions was suppressed and efficient 1.2?m emission was obtained.?4?Er³⁺ions-doped germano-gallate oxyfluoride glass-ceramics containing BaF₂nanocrystals were prepared through the exploration of glass compostitions,rare-earth ions doping concentration and melting procedure.With the incorporation of Er³⁺ions into BaF₂ nanocrystals,intense visible and infrared emissions were observed.Visible upconversion and infrared emission,especially the 2.7?m emission,were greatly enhanced.Most importantly,this type of glass-ceramics has high transparency up to⁵?m,indicating the potentitial as host materials to realize the mid-infrared emission from rare-earth ions.